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Refactor lower_stmts #87773

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Refactor lower_stmts #87773

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108 changes: 54 additions & 54 deletions compiler/rustc_ast_lowering/src/lib.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -64,7 +64,7 @@ use rustc_span::symbol::{kw, sym, Ident, Symbol};
use rustc_span::{Span, DUMMY_SP};
use rustc_target::spec::abi::Abi;

use smallvec::{smallvec, SmallVec};
use smallvec::SmallVec;
use std::collections::BTreeMap;
use std::mem;
use tracing::{debug, trace};
Expand Down Expand Up @@ -1787,22 +1787,22 @@ impl<'a, 'hir> LoweringContext<'a, 'hir> {
)
}

fn lower_local(&mut self, l: &Local) -> hir::Local<'hir> {
fn lower_local(&mut self, l: &Local) -> &'hir hir::Local<'hir> {
let ty = l
.ty
.as_ref()
.map(|t| self.lower_ty(t, ImplTraitContext::Disallowed(ImplTraitPosition::Binding)));
let init = l.init.as_ref().map(|e| self.lower_expr(e));
let hir_id = self.lower_node_id(l.id);
self.lower_attrs(hir_id, &l.attrs);
hir::Local {
self.arena.alloc(hir::Local {
hir_id,
ty,
pat: self.lower_pat(&l.pat),
init,
span: l.span,
source: hir::LocalSource::Normal,
}
})
}

fn lower_fn_params_to_names(&mut self, decl: &FnDecl) -> &'hir [Ident] {
Expand Down Expand Up @@ -2388,15 +2388,9 @@ impl<'a, 'hir> LoweringContext<'a, 'hir> {
}

fn lower_block_noalloc(&mut self, b: &Block, targeted_by_break: bool) -> hir::Block<'hir> {
let (stmts, expr) = match &*b.stmts {
[stmts @ .., Stmt { kind: StmtKind::Expr(e), .. }] => (stmts, Some(&*e)),
stmts => (stmts, None),
};
let stmts = self.arena.alloc_from_iter(stmts.iter().flat_map(|stmt| self.lower_stmt(stmt)));
let expr = expr.map(|e| self.lower_expr(e));
let (stmts, expr) = self.lower_stmts(&b.stmts);
let rules = self.lower_block_check_mode(&b.rules);
let hir_id = self.lower_node_id(b.id);

hir::Block { hir_id, stmts, expr, rules, span: b.span, targeted_by_break }
}

Expand All @@ -2414,50 +2408,56 @@ impl<'a, 'hir> LoweringContext<'a, 'hir> {
})
}

fn lower_stmt(&mut self, s: &Stmt) -> SmallVec<[hir::Stmt<'hir>; 1]> {
let (hir_id, kind) = match s.kind {
StmtKind::Local(ref l) => {
let l = self.lower_local(l);
let hir_id = self.lower_node_id(s.id);
self.alias_attrs(hir_id, l.hir_id);
return smallvec![hir::Stmt {
hir_id,
kind: hir::StmtKind::Local(self.arena.alloc(l)),
span: s.span,
}];
}
StmtKind::Item(ref it) => {
// Can only use the ID once.
let mut id = Some(s.id);
return self
.lower_item_id(it)
.into_iter()
.map(|item_id| {
let hir_id = id
.take()
.map(|id| self.lower_node_id(id))
.unwrap_or_else(|| self.next_id());

hir::Stmt { hir_id, kind: hir::StmtKind::Item(item_id), span: s.span }
})
.collect();
}
StmtKind::Expr(ref e) => {
let e = self.lower_expr(e);
let hir_id = self.lower_node_id(s.id);
self.alias_attrs(hir_id, e.hir_id);
(hir_id, hir::StmtKind::Expr(e))
}
StmtKind::Semi(ref e) => {
let e = self.lower_expr(e);
let hir_id = self.lower_node_id(s.id);
self.alias_attrs(hir_id, e.hir_id);
(hir_id, hir::StmtKind::Semi(e))
fn lower_stmts(
&mut self,
ast_stmts: &[Stmt],
) -> (&'hir [hir::Stmt<'hir>], Option<&'hir hir::Expr<'hir>>) {
let mut stmts = SmallVec::<[hir::Stmt<'hir>; 8]>::new();
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I don't know if 8 is optimal, but I think it is already used in the current implementation, in alloc_from_iter.

let mut expr = None;
for (i, s) in ast_stmts.iter().enumerate() {
match s.kind {
StmtKind::Local(ref l) => {
let l = self.lower_local(l);
let hir_id = self.lower_node_id(s.id);
self.alias_attrs(hir_id, l.hir_id);
let kind = hir::StmtKind::Local(l);
stmts.push(hir::Stmt { hir_id, kind, span: s.span });
}
StmtKind::Item(ref it) => {
stmts.extend(self.lower_item_id(it).into_iter().enumerate().map(
|(i, item_id)| {
let hir_id = match i {
0 => self.lower_node_id(s.id),
_ => self.next_id(),
};

hir::Stmt { hir_id, kind: hir::StmtKind::Item(item_id), span: s.span }
},
));
}
StmtKind::Expr(ref e) => {
let e = self.lower_expr(e);
if i == ast_stmts.len() - 1 {
expr = Some(e);
} else {
let hir_id = self.lower_node_id(s.id);
self.alias_attrs(hir_id, e.hir_id);
let kind = hir::StmtKind::Expr(e);
stmts.push(hir::Stmt { hir_id, kind, span: s.span });
}
}
StmtKind::Semi(ref e) => {
let e = self.lower_expr(e);
let hir_id = self.lower_node_id(s.id);
self.alias_attrs(hir_id, e.hir_id);
let kind = hir::StmtKind::Semi(e);
stmts.push(hir::Stmt { hir_id, kind, span: s.span });
}
StmtKind::Empty => {}
StmtKind::MacCall(..) => panic!("shouldn't exist here"),
}
StmtKind::Empty => return smallvec![],
StmtKind::MacCall(..) => panic!("shouldn't exist here"),
};
smallvec![hir::Stmt { hir_id, kind, span: s.span }]
}
(self.arena.alloc_from_iter(stmts), expr)
}

fn lower_block_check_mode(&mut self, b: &BlockCheckMode) -> hir::BlockCheckMode {
Expand Down